I am very new to Javascript.
I am having an error:

Uncaught TypeError: Cannot read property 'children' of null fiddle.jshell.net:1163
(anonymous function)

How to fix the error?

Providing my fiddle below:

http://jsfiddle.net/N3GTy/29/embedded/result/

var slider = new Swipe(document.getElementById('slider'), {

    callback: function(e, pos) {



        var i = bullets.length;

        while (i--) {

            bullets[i].className = ' ';

        }

        bullets[pos].className = 'on';



    }

}),



bullets = document.getElementById('position').getElementsByTagName('em'),



// tabs

tabs = new Swipe(document.getElementById('tabs'), {

    callback: function(event, index, elem) {

        setTab(selectors[index]);

    }

}),



selectors = document.getElementById('tabSelector').children;

Uncaught TypeError: Cannot read property 'children' of null



for (var i = 0; i < selectors.length; i++) {

    var elem = selectors[i];

    elem.setAttribute('data-tab', i);

    elem.onclick = function(e) {

        e.preventDefault();

        setTab(this);

        tabs.slide(parseInt(this.getAttribute('data-tab'), 10), 300);

    }

}